IKEA has all their catalogs, 1950–2021, online, which should represent a unique slice of time of what is popular within interior design. IKEA worked with customer feedback from the start in order to sell just the right products and based on their success over the years (see mail-in form from the 1955 catalog to the right), it seems safe to say that IKEA has consistently offered what people want.
The question emerges if one could sort of reverse this process and pick up general design trends from the catalogs. For example how selections of fabrics, patterns, and wood types have shifted over time. Here, the idea is to try to pick up trends in color from the catalogs. One can imagine that both colors of the products in the catalog as well as the design of the catalog itself will follow (or drive) what is popular.
Every catalog page is a high-resolution jpeg-encoded scanned image, e.g. the first page of the 1950 catalog: